Elephants and Komodo dragons in Australia? Bears and wolves roaming freely throughout European villages and towns? It might sound a bit far-fetched, but this all fits within a new strand of conservation theory known as Rewilding.

With ancient megafauna lost, and with our remaining large animals pushed further and further towards extinction, conservation theorists are looking at introducing the few large creatures we have left back into the wilderness to stimulate and restore ecosystems.

And he's asking us to think big. Just how big? Well, roughly the size of an African elephant....

David Bowman: Rewilding is actually restoring ecological processes to make ecosystems sustainable because we have to choose now, because we can't just stand back and allow, say, the equivalent of a biological catastrophe of, for instance the spread of the gamba grass. What are we doing about it? We're not doing anything about it. We have to step up and to realise that these plants are going to take their opportunities, and we have to fight back using a known proven tool, which is a big herbivore.

Carl Elliott Smith: That was David Bowman, Professor of Environmental Change Biology at the University of Tasmania. Last year Professor Bowman argued in an article in the scientific journal Nature that Australian ecosystems would benefit from the introduction of elephants and Komodo dragons. Why? Well, he believes that these large keystone species may be able to help revitalise our damaged environment.

His argument is based on a conservation theory called rewilding. Rewilding is focused on restoring balance to our remaining ecosystems. It builds on top of basic conservation theory and focuses on reintroducing ecologically important species that are missing in the wild, such as wolves or bears in North America.

However, what makes rewilding controversial is the notion that similar non-native animals should be used as substitutes if the original species can't be reintroduced. For example, an African lion or another large cat could be used to replace the now extinct European lion. And because we can't bring the Tasmanian tiger back to life, perhaps another top predator such as the Komodo dragon would suffice.

Dr Josh Donlan is the Director of Advanced Conservation Strategies and is a visiting fellow in the Department of Ecology and Evolutionary Biology at Cornell University.

Josh Donlan: Rewilding has its start in North America in the late 1980s, and the term was coined by Michael Soulé and Dave Foreman, and that became a movement focused on three main pillars; large protected core reserves, connectivity, and keystone species. And that started a movement to think about continental level conservation starting in North America and then moving quickly into Europe, to Australia and other places. And it was largely focused on the disproportionately important role of keystone species, most often large predators and large herbivores. Pleistocene rewilding built on that, took that vision and took a long historical view and asked the question; should we consider reintroducing species, sub-species or closely related species to help restore very important functions within the ecosystem?

Carl Elliott Smith: So rewilding looks at a larger ecological picture to figure out which processes are missing in our remaining ecosystems. To maintain and preserve those species still alive today, its proponents are even willing to bring in non-native species to the plug gaps. Here's Dr Donlan again:

Josh Donlan: Rewilding is part of I would say a growing movement that takes a more proactive approach and is much more based on restoration as opposed to preservation, and the importance of that revolves around trying to restore processes as opposed to being strictly focused on trying to stop species extinctions. And that's part of the controversy around that, both in the public sphere and the scientific sphere.

Carl Elliott Smith: So mechanistically how do you rebuild processes into an ecosystem by bringing in new animals or new species?

Josh Donlan: So we have quite a few very good well-documented examples of the ecosystem and ecological benefits of reintroducing either predators or large herbivores to ecosystems. Here in North America probably the most celebrated and well studied example is wolves in Yellowstone. Wolves were extirpated by humans earlier this century and then they were reintroduced a few decades ago into Yellowstone, and as a result of that, wolf predation affects that ecosystem not only by affecting the large herbivores they prey on but also affecting the plant distribution because the herbivores changed the way they forage on plants and so these top trophic level predators have an impact on the ecosystem that cascades throughout the ecosystem all the way down to the plant level.

And so we now know from that example and other examples in Africa and elsewhere that this big stuff, the large predators, large herbivores, play really important roles, which ask the question; should we think about bringing them back? Because if we look back in history, deep history, say in the last 13,000 years, we know there was a lot more big stuff around, there was a lot more big stuff in Australia, there was a lot more big stuff in North America, and there was a lot more big stuff in Europe. Most of those species are now either extinct or drastically reduced, for a variety of reasons, mainly almost all anthropogenic. But some of those species that are collectively referred to as mega-fauna still exist, and now people are starting to think about can we reintroduce them, does it make sense to reintroduce them from an ecological perspective and an evolutionary perspective, and even a socio-economic or aesthetic perspective.

Carl Elliott Smith: What kind of empirical evidence do we have for whether or not Pleistocene rewilding could work?

Josh Donlan: There's a handful of efforts around the world, largely focused in Europe and Asia and on islands. Some of those have been ongoing for a while, some of them are newer and being planned as we speak. Probably some of the best scientific evidence that justifies the idea of rewilding and using closely related species to function as analogues for extinct species come from islands.

Carl Elliott Smith: And in 2011 a study on a small island off the coast of Mauritius showed in a controlled setting that rewilding can actually work.

Stephen Harris is Professor of Environmental Sciences at the University of Bristol. He and his colleagues introduced non-native tortoises to this island to replace the extinct native variety. This study is being touted as the first empirical example of rewilding working as a mechanism for conservation.

Can you tell us about the island Ile aux Aigrettes? Where is it, how big is it, and how did I go with the pronunciation of its name?

Stephen Harris: You did pretty well, at least that's how I pronounce it. It's a small coralline islet just off the coast of Mauritius. It's within the coral atoll, so it's only about 500 metres off the coast, and it's a small island, it is only about 25 hectares. So it's interesting because it's a small ecosystem that you could manage, and I have to say that the island is actually managed by the Mauritian Wildlife Foundation who have spent a long time trying to recreate the lowland ebony forests that used to dominate much of lowland Mauritius on this small islet. So it's an interesting little ecosystem.

Carl Elliott Smith: You brought up the endemic ebony trees there on the island, but could you explain explicitly for us, what was the problem with this local ecosystem?

Stephen Harris: Well, originally it was dominated by alien plants and had been used as an island to breed goats on, so various alien plants had been introduced to feed the goats. And Mauritian Wildlife Foundation for a long time have been clearing the island of alien plants and had a nursery on the island where they are growing up seeds of native plants and planting them out on the island.

Now, for some species that was all right, but really you're trying to get a functioning ecosystem that rather looked like the original ecosystem that was there, but of course that they had no seed dispersal, there was none of the big species that used to disperse seed. Originally Mauritius was famous for various species, such as the dodo which was a flightless pigeon that dispersed big seeds, lots of parrots, some of them were quite big, one or two really big terrestrial parrots that also dispersed large seeds and fruits.

And it was also done by two species of giant tortoise that lived on the islands, and they were exterminated back in the late 1700s. So all the species that disperse seeds naturally had largely gone, and so the idea was trying to see whether we could recreate an ecosystem whereby seed dispersal was a natural process.

Carl Elliott Smith: So you were aiming to re-wild this island then using a non-native tortoise species, correct?

Stephen Harris: That's right. The whole of the Mascarenes, that's basically Mauritius, Rodrigues and Réunion, had between them five species of giant tortoise that were a genus that was endemic to these islands. There were two different species on the island and Mauritius. They were exterminated, so we had no living relatives or close relatives to these tortoises that had been exterminated, so the only option was to see if you could find what you might call an ecological analogue or a taxon substitute, a closely related species. The one we've chosen, the Aldabran tortoise, is actually a dome-backed tortoise that looked much the same as the original native species, and functioned in the same sort of way, that could actually fill the gap in the ecological processes that the native tortoises fulfilled.

Carl Elliott Smith: So let's talk about what happened then when you introduced this exotic species. What happened to the endangered ebony tree?

Stephen Harris: Well, it's very good because straight away the tortoises started eating the fallen fruits, and what you found is that the fruits that had gone through the tortoises' guts had much higher germination rates and also germinated much faster. And of course fast germination is important because if you're in an environment where you have limited rainfall seasons, the seedlings have to get established fast so that they can actually make the most of the rain before the environment changes against them.

So these tortoises were both helping the germination and survivability of the seeds but also rapidly spreading them across the island because much of the ebony had been cleared off the island for fuel back in the past, so trying to re-establish native ebony trees across the island was a key goal for the project.

Carl Elliott Smith: In the paper you've released on this you describe that you've been able to revive an extinct ecological interaction. Could you talk a little bit about that for us?

Stephen Harris: Well, one of the big problems in Mauritius is that a lot of the seed dispersers have gone and a lot of the pollinators have gone, all the species that played these key roles. And if you think about ecosystems, they consist of complex food webs, species that depended on each other for various biological functions. Once you take one or two species out of that food web, then around them you get lots of cascades of extinction, other species disappear. And these cascades last several hundreds or a few thousand years until the ecosystem settles back into a much more depauperate ecosystem.

So if you can act quickly, and remember these tortoises didn't disappear that long ago, if you can plug those gaps fairly quickly, then hopefully the aim is that in the long term you will reduce the number of species you lose in those cascades of extinction. That's really what we mean by this ecological interaction; we plug the holes in that food web to try and prevent other species going extinct.

Carl Elliott Smith: Although rewilding has been shown to work on a short timescale and in a small, isolated geographical area, many traditional environmentalists are happy to trial the idea as it also provides new safe havens for vulnerable species such as the Aldabran tortoise.

However, it's not just those with environmental interests who have adopted the idea. Rewilding Europe is a not-for-profit organisation that aims to find a way to build jobs around the reintroduction of wild animals into Europe, for example via ecotourism, safari parks or even potentially 'wild' meats. The organisation aims to have 1 million hectares, or 10,000 square kilometres, by 2020, and they're already well on their way to that goal, with five reserves already up and running, and another five to be announced later this year.

Frans Schepers: My name is Frans Schepers, the managing director of Rewilding Europe which is a new initiative in Europe with the aim to make Europe a wilder place, which means more space for wilderness, for wild nature, for wildlife, not only for a conservation benefit but also for the people who were living in areas which are now being abandoned and where this approach might provide a very nice new opportunity for them and where people can benefit from wild nature.

Carl Elliott Smith: Could you explain the genesis of Rewilding Europe to us?

Frans Schepers: Well, the idea of Rewilding Europe actually started when a number of people realised that indeed there is huge land abandonment happening in Europe because young people move to cities, urbanisation, we know that from all over the world, but it's definitely happening in Europe on a large scale, especially from let's say more marginal agricultural areas. It is expected that in 2015 four out of five Europeans will live in urban areas, which means that huge land areas become available, and this triggered our idea, well, maybe this is an incredible opportunity to increase our natural areas.

Carl Elliott Smith: Just how wild are we talking here? There are different approaches to rewilding. What does a rewilded Europe look like to your organisation?

Frans Schepers: Yes, our slogan actually is Making Europe a Wilder Place, and what we would like to do is to move on this scale of wildness to a more wilder state. So rewilding is a very active process where we would like not people managing and shaping the landscape but actually nature itself. So it's very much about allowing and stimulating natural processes to take their course, and we would like to bring wildlife back to natural numbers where they can play their role in our ecosystems, but also where they could become a drawcard for, for instance, wildlife watching tourism, which is at the very early stages now in our continent.

Carl Elliott Smith: Is your goal conservation or is it something a little bit different?

Frans Schepers: Well actually, rewilding, you could see it as a new tool for conservation which is traditionally very much conserving, it has a very defensive and conserving approach. What we're actually doing is…call it restoring ecosystems, where natural processes take their own course. That's pretty revolutionary for Europe because man has the idea that if we don't manage nature then it won't work, and that is of course not true.

But I think one of the key differences with a lot of other conservation initiatives is I think the business component. You know, how can we make rewilding, wild nature also beneficial to people in a very direct way? So the enterprise component is something that makes our initiative unique I think, and because we are very actively working to provide benefits to people that live in those areas and who are actually suffering very much from this land abandonment. Because if you speak to a mayor in the Romanian Carpathians and he's telling you, well, the last five years half of my population in my village disappeared, we had to close the school, we had to close the library, there are two children born…I mean, it's a very dramatic situation in some of these areas and people are desperate. And so we are not a traditional conservation initiative because through this we also very actively work on providing new opportunities, turning threats into opportunities through the rewilding process.

Carl Elliott Smith: Although Rewilding Europe does well, at least in theory, to walk the line of rebuilding the environment and providing jobs, it's not without its risks. The reserves they've established are open and unfenced, often bordering on nearby villages. And the animals being rewilded include bears, wolves, carrion, other mid-range carnivores, and even giant bovine, similar to the extinct aurochs.

Frans Schepers: Actually none of these species are dangerous, not at all. So the wolf is not dangerous, the bear is not dangerous. That sounds maybe a bit strange but people have always these pictures of these dangerous animals, but statistics show that…like in Scandinavia there were 27,000 human-bear encounters, and actually only once or twice there were problems. With wolves, never any problems in Europe. We have about 18,000 wolves now in Europe. The brown bear is much more, it's like 25,000.

And a species like the aurochs, if you think about the Spanish fighting bull, yes, that's an aggressive animal because it has been selected over hundreds of years, bred looking for, you know, the more aggressive the better. But actually we are working already with a lot of these ancient cattle races and naturally those are very friendly animals. The problem is that people…that could of course happen if you approach them too closely and you get between the mother and the calf, for instance. Well then there could be of course some defence. But these animals never approach or attack people.

Carl Elliott Smith: A lot of Rewilding Europe aims to rebuild areas that are quite close to urban centres. So how do you go about containing these rewilded areas?

Frans Schepers: Yes, these are actually open systems of course, so we are not looking at fenced reserves, but of course maybe in some villages you should maybe have a fence to keep animals out. But actually we should not exaggerate now, we are talking about huge areas where there is a lot of space and where animals also will de-domesticate. You know, some of these, like the aurochs-like animals, they will go, and we have seen it with others, go through a de-domestication process and become wilder and wilder. They will run away from people, they will have to learn how to defend themselves against wolves. So I'm not afraid at all of animals coming close to cities in terms of becoming dangerous.

Actually if you look at several polls that were done among the general public about would you like the wolf, for instance, to come back to the Netherlands, and polls showed in the general public that the majority of the people, more than 80%, welcomes the wolf. So the public attitude towards wilderness, the tolerance with animals, is also becoming more positive and it is really changing.

Josh Donlan: One of the biggest challenges to rewilding is the social implication and social challenges and the fact that people don't like large animals, to a certain extent. My response to that is go to Africa, people deal with large animals all the time. Go to India, they are cohabiting. There are a lot of challenges around it, there's a lot of research around it, and people are learning methods and techniques to cohabitate with large animals. So you could make the counter argument that should we just expect the continents of Africa and India to uphold and maintain the world's remaining mega-fauna? So it's a challenging question.

I don't buy the criticism that we can't expect communities to learn to coexist with large animals. And it gets to the point that in my experience while we have this great fear of large animals, you also have this great love of large animals. There are important reasons why our sports teams and our cars are named after large animals, and that relationship goes back thousands of years into the human psyche. And so one can make the argument that this idea of restoring ecosystems and being proactive with large herbivores and large predators could jumpstart biodiversity conservation in general, give it some uplift, because humans relate, both in a positive and sometimes negative way, but they certainly have a special relationship with large animals.

Carl Elliott Smith: Just to re-cap, today we're exploring the idea of rewilding as a mechanism to rebuild current ecosystems and to provide new homes for dwindling and endangered species. We've heard about the first empirical studies of rewilding in small island settings, and we've also heard about a vision for a wilder Europe and North America.

Now, as promised, we'll return to Professor David Bowman from the University of Tasmania to hear about his ideas for rewilding Australia. He argues that big problems require big solutions. And introducing elephants and Komodo dragons isn't such a strange idea if you think about the mega-fauna that once roamed our continent and the role they played in the ecosystem.

David Bowman: I think we've got to go to prehuman Australia, and once you get your mind around the fact that 40,000 to 50,000 years ago Australia had a diverse large mammal assemblage, and that diverse large mammal assemblage had a massive transformative effect on our landscapes and on our vegetation structure and patterns and fire activity.

Aboriginal people, coincident with their arrival and probably for lots of reasons, not just over-hunting and burning, the large animal assemblage disappeared. The Aboriginal populations were able to sustain Australia by hunting and burning. Their hunting and burning were very closely coupled. We've disrupted that and then added in these new plants and new animals. So we've got a very mixed-up ecology, if you will.

So what I'm envisaging is that we have to look at our major threatening processes and to think about how we could get these ecosystems back into some sort of stability. I'm not saying I've got the answer, obviously this is leading-edge debate. We've got to debate these things and, I would like to think, trial these things, because this is how we're going to learn. As we're going into the 20th century we're going to have to do this as a global project to stabilise dysfunctional ecosystems. Human beings, like it or not, are undertaking massive ecological engineering programs. That's what we're doing, particularly because we are contributing to rapid climate change.

So with, say, an out-of-control grass like gamba grass, it was introduced to feed cattle. Cattle can't eat a grass when it grows three metres high. If you actually think about it, a lot of these uncontrolled grass fire cycles are really telling us that the animals that should be consuming that grass are missing, so we should try to put back animals that are large enough to process this biomass which would then reduce the out-of-control fires, would reduce the spread of the grasses, and we would wind up with a new ecosystem.

So I'm on the utilitarian side, I'm saying these large animals…rewilding is actually restoring ecological processes to make ecosystem sustainable because we have to choose now, because we can't just stand back and allow, say, the equivalent of a biological catastrophe of, for instance, the spread of gamba grass. What are we doing about it? We're not doing anything about it. We have to step up and to realise that these plants are going to take their opportunities, and we have to fight back using a known proven tool, which is a big herbivore.

Carl Elliott Smith: Of course elephants are the large herbivore replacement that Professor Bowman is talking about. And even though Komodo dragons are his controversial suggestion for a replacement top predator, he says that if that idea is too unpalatable, then humans could potentially fill the same gap.

David Bowman: We're going to have to re-understand if we don't want to put a dangerous large predator back into our landscapes, we need to have humans as hunters. And I certainly know Aboriginal people are extremely good hunters, they own a lot of land, and one of the things that they could be encouraged to do through the emerging ranger programs that are developing in Aboriginal communities right across northern Australia, is to be used as the top predator to control the numbers of the invasive animals.

The thing about ecological systems is that these processes are 24/7, they are there, they're running, they're regulating, they're controlling the system, whereas a lot of land management activities are just bursts of activity, the funding dries up, everybody goes away, whereas what we could be doing is a lot smarter, is having people going out into the bush being the top predator. If the cost of labour is too much, well, another view, a dangerous view, is to say, well, we'll get another species to do it.

Carl Elliott Smith: Critics of rewilding argue that introducing new species into our already fragile ecosystems will cause more problems than it solves. In Australia especially we've seen the dangerous effects of introducing exotic invasive species.

However, like Professor Bowman, Dr Donlan from Cornell University argues that we should at least explore and trial rewilding as a mechanism for conservation, because for many endangered species time is running out.

Josh Donlan: In my view we now impact almost every square inch on the world, and whether we're going to do so either by default or design, and not doing action is not without its consequences. And so I think we've learned a lot over the past 50 years with fields of conservation biology, with the fields of restoration biology, that we can do restoration and we can do re-introductions strategically, smartly, and scientifically based. And we now have lots of examples of that in terms of being able to restore ecosystem processes, being able to restore ecological processes, being able to restore ecosystems for that matter.

Antony Funnell: Dr Josh Donlan there from Cornell University, and he was speaking with freelance producer Carl Elliott Smith.

Next week on the show – we begin the first part of our four part special series on space and off-earth exploration. The first show is about astronomy – don’t miss it.

Thanks to Jim Ussher and Andrew Davies – the other members of the production team. I’m Antony Funnell – until next week - cheers and bye for now.

Guests

Dr Josh Donlan

Director of Advanced Conservation Strategies and Visiting Fellow in the Department of Ecology and Evolutionary Biology at Cornell University.

Stephen Harris

Professor of Environmental Sciences at the University of Bristol.

Frans Schepers

Managing Director of Rewilding Europe.

David Bowman

Professor of Environmental Change Biology at the University of Tasmania.